Houston, an reservoir located approximately northeast of Downtown, was created by damming the San Jacinto River in the 1950s to create a dependable, long-term supply of drinking water. The lake is owned and operated by the City of Houston. Besides supplying water to the city, the lake is also a central feature of the Kingwood community and serves as a recreational destination. Galveston Bay is a central feature of the Greater Houston metropolitan area. The bay serves an essential economic role as the home of the Houston Ship Channel and a large fishing industry and is also an important destination for recreation and coastal wildlife. Covering approximately , the estuary extends inland from the coast and has a maximum width of . Important regional communities, including Galveston and Texas City, are located along the bay. While the City of Houston proper does not adjoin the bay, its limits do extend southward to encompass the NASA Johnson Space Center and the community of Clear Lake. Clear Lake, which gives the aforementioned community its name, is a tidal lake with brackish water located on the western side of Galveston Bay. Covering about , the lake is fed by Clear Creek and inflow from the bay. Ultimately, the Clear Creek watershed covers an area of encompassing seventeen tributaries. Groundwater Two freshwater aquifers, the Chicot and Evangeline, underlie the Greater Houston area. These aquifers are composed mostly of sand and clay. The Chicot is located above the Evangeline, and a confining layer separates them from the Jasper aquifer below, which is mostly saltwater. A majority of drinking water supply wells in Houston are drilled to depths between and . Extraction of water, oil, and gas from these aquifers has caused land subsidence throughout the Greater Houston region since the early 20th century. Before 1942, Houston's municipal water supply was sourced exclusively from groundwater wells. The inception of the petroleum industry at the beginning of the century also led to widespread resource extraction around the city. Surface elevations began to drop with the water table, and by the 1970s, areas around the Houston Ship Channel had subsided up to due to rapid industrialization, prompting the creation of the Harris–Galveston Coastal Subsidence District. By the end of the decade, subsidence had intensified to in some parts of east Houston, and of the region had experienced at least of sinking. The creation of the district, which enforced